Animal viruses initiate their replicative cycles by attaching to a cellular membrane receptor, followed by entry into the cell. Identification of the poliovirus receptor, Pvr, was essential for the establishment of a transgenic mouse model for poliomyelitis. Although a great deal is known about the pathogenesis of poliovirus infection, relatively little is understood about how echoviruses cause disease. Echoviruses are important human pathogens and are responsible for aseptic meningitis, neonatal sepsis, myocarditis, exanthemas, respiratory illness and gastrointestinal disease. Because most echovirus strains only replicate in humans, a mouse model has not been available for studying echovirus pathogenesis. The object of work in this proposal is to isolate transgenic mice that express human cell receptors for echovirus, to establish a new animal model for studying echovirus pathogenesis. We propose to isolate transgenic mice that express VLA-2, a heterodimeric integrin consisting of alpha2 and beta1 subunits, which is known to be the cell receptor for echovirus types 1 and 8. Three specific aims are planned. First, human cDNA encoding the alpha2 and beta1 subunits of VLA-2 will be placed under the transcriptional control of the human beta-actin promoter, and used to establish transgenic mice that express both proteins. Second, tissues and organs of VLA-2 transgenic mice will be examined by Northern and Western blot analysis and immunohistochemistry for expression of VLA-2 RNA and protein. Third, the susceptibility of VLA-2 transgenic mice to echovirus type 1 infection by different routes, as well as the location of virus replication after inoculation, will be determined. In addition, the ability of echovirus to spread from muscle and intestine to the central nervous system by axonal transport will be determined. Fourth, experiments will be done to determine if an immune response is mounted during echovirus 1 infection of VLA-2 transgenic mice. Knock-out mice will be used to study the role of the immune response in limiting or exacerbating echovirus pathogenesis. Transgenic animal models would enable studies on the sites of echovirus replication, the mechanisms of viral spread, and the basis of echovirus tissue tropism. Establishment of a small animal model may yield information about echovirus pathogenesis that could stimulate development of echovirus vaccines or antiviral drugs.